<html xmlns="http://www.w3.org/1999/xhtml" xmlns:m="http://www.w3.org/1998/Math/MathML">
<head>
<script>

function boom()
{
  document.getElementById("td").contentEditable = "true";
  document.execCommand("justifyfull", false, null);
}

</script>
</head>
<body onload="boom();">
<m:msubsup><td id="td"><m:mn/></td></m:msubsup>
</body>
</html>
